The Kewaunee County Land & Water Conservation Committee this week got a briefing on the study of a random group of private wells in the county that has been ongoing for three years now.
Dr. Mark Borchardt, a Marshfield-based microbiologist for the U.S. Department of Agriculture, is completing a paper to be peer-reviewed and submitted to a technical journal, probably later this year, aimed at identifying risk factor for private well contamination using statistical models.
Depth to bedrock “turns out to be a very, very important parameter.”
He has been compiling data from the random sampling of 621 private wells in the county. Research released in 2017 indicated about 208 of those wells showed contamination from bacteria or high nitrate levels, and a review of the pathogens in the contaminated wells showed levels well above the state average. There was evidence of both bovine and human waste in the affected wells.
The studies have shown that the depth of topsoil to bedrock seems to play a key role in contamination. Preliminary findings were used to establish state and local standards regarding the spreading of manure on farm fields where soil is 0-20 feet deep over fragile Silurian dolomite or karst bedrock.
Another major factor is heavy rainfall within seven days before the well test, which can wash contaminants into the aquifer.
Borchardt presented data that he said concludes that risk factors for private well contamination include the existence of septic systems within 750 feet of the well; agricultural fields under nutrient management plans within 750 feet; and proximity to manure storage facilities, such as lagoons, and septic system drain fields.
“I don’t have an agenda,” Borchardt said as he opened his presentation. “I follow the data … my job requires that I have no opinion.”
As a result of the data and analysis, “we can provide policy makers and stakeholders with ideas for prevention,” he said. “We can look at setback distances, we can look at allowable densities and number of contamination sources, we can look at vulnerable periods related to weather, and we can look at well construction best practices. I can give you this information, but then it’s up to the officials, policy makers, to decide these things.”
Later he acknowledged that he planned to make a presentation later in the day to Peninsula Pride Farms, a group of Kewaunee and Door county farmers that has been working on ways to prevent groundwater contamination through tactics like planting cover crops and other best management practices.
“Whoever invites me, I’ll speak,” he said. “I don’t care what your agenda is or your politics or any of that. If I get invited, I go speak. Doesn’t matter.”
A Door County group has invited him to talk about his team’s findings on June 19, and Land & Water Chairman Chuck Wagner said plans are in the works for a public presentation this spring by Borchardt and UW-Oshkosh geologist Maureen Muldoon. The two scientists offered a similar program in June 2017.